HYDROPHOBIC CIS-PLATINUM COMPLEXES EFFICIENTLY INCORPORATED INTO LIPOSOMES

摘要

The present invention concerns a platinum (II) four-coordinant complex having the formula: wherein R1 is an alkyl diamine or cycloalkyl diamine and R2 and R3 are an alkylcarboxylato containing from five to ten carbon atoms. The R1 is preferably trans-D,L-1,2-diaminocyclohexane, trans-R,R-1,2-diaminocyclohexane, trans-S,S-1,2-diaminocyclohexane, cis-1,2-diaminocyclohexane ethylene diamine or 1,1-bis(aminomethyl)cyclohexane. The R2 and R3 are preferably neohexanoato, neoheptanoato, neononanoato, neodecanoato, neooctanoato, neopentanoato, 2-ethylhexanoato, 2-ehtylbutyrato, 2-propylpropanoato, 2-methyl-2-ethylheptanoato, 2,2-diethylhexanoato, 2,2-dimethyl-4-ethylhexanoato, 2,2-diethyl-4-methylpentanoato, 2,2-dimethyloctanoato, 2-methyl-2-ethylheptanoato, 2,2-diethylhexanoato, 2,2-diethyl-4-methylpentanoato or 2,2,4,4-tetramethylpentanoato. In an important further aspect, the present invention involves preparation and therapeutic use of a liposome comprising a phospholipid and a four-coordinate platinum complex having the formula: wherein R1 is an alkyl diamine or cycloalkyl diamine and R2 and R3 are an alkylcarboxylato containing from about five to about fourteen carbon atoms. The R1, R2 and R3 functions are preferably as described above with the exception that R2 and R3may have even longer alkyl chains such as myristate and laurate, i.e., up to fourteen carbon atoms. For therapeutic use, a pharmaceutical composition comprising this liposome and a pharmaceutically acceptable carrier or diluent may be readily prepared by methods well known to those skilled in the art. The liposomes are useful vehicles for solubilizing the otherwise aqueously insoluble complexes of the present invention. The phospholipids of the liposomes may be one or more of phosphatidylglycerol, phosphatidylcholine, sphingomyelin, phosphatidic acid or phosphatidylserine. The liposomes more preferably consist essentially of phosphatidylglycerol, phosphatidylcholine or a combination thereof and may also comprise cholesterol. The liposomes of the present most preferably comprise phospholipid consisting essentially of dimyristoylphosphatidylglycerol, dimyristoylphosphatidylcholine or a combination thereof.